Absence Of Emulsifier Research Articles

Kinetic Model for the Hydrolysis of Olive Oil by Lipase in Absence of Emulsifier

Kinetic Model for the Hydrolysis of Olive Oil by Lipase in Absence of Emulsifier

Emulsifier-free emulsion polymerization of acrylonitrile-butadiene-carboxylic acid monomers: a kinetic study based on polymerization pressure profile

Emulsion polymerization of acrylonitrile-butadiene-carboxylic acid monomers (XNBR latexes) in the absence of emulsifier is associated with thermodynamic and kinetic complexities and is very sensitive to colloidal stability. In this paper, polymerization pressure profiles were utilized for kinetic studies of emulsifier-free emulsion terpolymerization of acrylonitrile, butadiene and two carboxylic acid monomers (i.e., acrylic acid and methacrylic acid). It was found that the type and amount of acidic monomer have a great impact on the nucleation rate as well as particle size distribution and carboxyl group distribution of XNBR latexes. Also, the type of the acidic monomer affects the rates of entry and exit of radicals to and from particles and consequently the average number of radicals per particle, where a higher rate of polymerization was observed for methacrylic acid latexes. The reaction temperature has profound effects on polymerization rate, particle size distribution and colloidal stability of the latex. Partitioning of pressure profiles into four distinct regions in accordance with well-established intervals of Harkins model and analyzing particle size distribution and carboxyl group distribution, established a conceptual framework for kinetic studies in emulsion polymerization of XNBR latexes.

Waterborne acrylic–casein latexes as eco-friendly binders for coatings

Abstract The use of casein as renewable resource to produce eco-friendly hybrid latexes has an increasing importance in industrial applications especially for high performance waterborne coatings. This work describes the synthesis of hybrid acrylic–casein latexes by emulsion polymerization of acrylic monomers in presence of varied casein concentration, and in absence of emulsifier which is usually a challenge for preparing stable nanocomposite latexes. The production and microstructure characterization of the casein–acrylic nanoparticles, as well as the properties of the films obtained from the hybrid latexes are here reported. The synthesized acrylic–casein latexes are able to form films with promising properties for a potential application as waterborne bio-based coatings.

Impact of Various Parameters Over the Stability of Water-in-Vegetable Oil Emulsion

Theory regarding emulsification, its coalescence and impact of emulsifier over its stability has been updated. For the verification of the proposed theory, water-in-oil emulsion was prepared by mixing water and soybean oil in the presence and absence of emulsifier, monoglyceride. The effect of different parameters like emulsification time, contents of water, and concentration of emulsifier has been investigated on the emulsification and coalescence process of the emulsion. It was noted that the emulsion quality was highest if the mixture was homogenized for about 15 minutes and the water contents were 40% v/v. The addition of monoglyceride up to 0.5% w/v gave the most stable emulsion having higher quality than other composition. The results obtained were compared with the proposed theory and found to have good compositions.

Distribution of catechol in emulsions

In this work, we have evaluated the effects of emulsifier concentration on the distribution of catechol (1,2‐dihydroxybenzene, CAT) in food‐grade emulsions composed of stripped corn oil, acidic water, and Tween 20. Auxiliary experiments in binary stripped corn oil–water mixtures, in the absence of emulsifier, showed that CAT is both oil and water soluble (partition constant = 0.34). Addition of Tween 20 to prepare kinetically stable emulsions creates an interfacial region, and the distribution of CAT is now described by two partition constants, that between the oil and interfacial region, , and that between the aqueous and interfacial region, . These partition constants were determined in the intact emulsion by employing a kinetic method that exploits the reaction between the hydrophobic 4‐hexadecylbenzenediazonium ions, 16‐ArN2+, and CAT. Results show that CAT distributes between the three regions. At emulsifier volume fractions of ΦI = 0.005, CAT is predominantly located (~61%) in the aqueous region, about 26% is in the interfacial region, and only a small fraction (~13%) in the oil region. An increase in emulsifier concentration promotes the incorporation of CAT to the interfacial region up to ~70% at ΦI = 0.037. Results obtained should contribute to a better understanding of the antioxidant efficiency in inhibiting lipid oxidation and to the development of new strategies to prepare healthier and more nutritional foods with longer shelf life. Copyright © 2013 John Wiley & Sons, Ltd.

无皂种子乳液聚合制备新型增稠剂

采用无皂种子乳液聚合方法制备了一种新型丙烯酸酯共聚物增稠剂。为了获得表面清洁和表面富含羧基的功能性聚合物乳胶粒子，首先合成了种子颗粒直径在250~300纳米的聚(苯乙烯-甲基丙烯酸)(P(St-MAA))种子乳液；然后，在无乳化剂的条件下，聚合丙烯酸乙酯(EA)，甲基丙烯酸十二酯(LMA)，苯乙烯(St)和甲基丙烯酸(MAA)；最后，得到颗粒直径在380~440纳米的稳定乳液。重点研究了甲基丙烯酸十二酯含量对乳液颗粒大小和乳液稳定性的影响。研究表明，该聚合物乳液具有很好的增稠性能，良好的悬浮能力，透明性好，易于使用。采用傅里叶变换红外光谱仪(FT-IR)、示差扫描量热仪(DSC)、透射电子显微镜(TEM)对其结构和形貌进行了表征。 A kind of acrylates copolymer thickener was prepared by soap-free and seeded emulsion polymerization. In order to obtain functional polymer latex particles with clean surface and with surface carboxyl groups, Poly (styrene-methacrylic acid) (P (St-MAA)) seed particles with the diameter of 250 - 300 nm were synthesized via soap-free emulsion polymerization. Then the seeded emulsion copolymerization of ethylacrylate (EA), lauryl methlacrylate (LMA), St and MAA onto the seed particles were performed in the absence of emulsifier. The content of LMA effected for the particles size and the stability of the emulsion was studied. The thickening performance of this polymer latex was quite good with the high thickening performance, good suspension ability, good transparence and easy to use. The factors of the copolymerization and the properties of the emulsion were discussed. Its structure and morphology were characterize by fourier transform infrared spectrometer (FT-IR) and transmission electron microscope (TEM).

Indomethacin Nanoparticles for Applications in Liquid Ocular Formulations / Наночастицы С Индометацином Для Применения В Жидких Лекарственных Формах Для Глаз

Studies in recent years have consistently shown that polymeric drug nanocarriers can be used in drug release and drug delivery systems to treat eye disorders. To achieve effective control over drug delivery, it is of crucial importance what kind of polymer and which method for drug inclusion in the nanoscale carrier we choose and what conditions are needed for the performance of this process. The aim of this study was to produce poly(vinyl acetate) nanoparticles with indomethacin incorporated in them, assess the effect of time for dialysis of the residual monomer and initiator on the degree of incorporation of indomethacin in the nanoparticles and on the kinetics of its release, to include them in ophtalmic formulations. Poly(vinyl acetate) nanoparticles with indomethacin were obtained by emulsion radical polymerization of vinyl acetate in the presence of indomethacin (in situ inclusion) and the absence of emulsifier. To release the residual monomer and initiator (ammonium persulfate) the obtained latexes were dialysed for 6, 9, 18 and 23 hours and then the nanoparticles were freeze-dried. Structural analysis was performed by transmission electronic microscopy, infrared spectroscopy, differential thermal analysis and thermogravimetry. Release of indomethacin was observed using ultraviolet spectroscopy. We proved the delayed release of indomethacin from the poly(vinyl acetate) nanocarrier and the lack of chemical interaction between the polymer and indomethacin. After 9-hour dialysis the initiator and the residual vinyl acetate were removed from the nanoparticles, while the entrapped indomethacin kept therapeutic concentrations. Dialysis for more than 6 and no more than 9 hours is recommended to remove the residual monomer and initiator when preparing indomethacin nanoparticles by in situ radical emulsion polymerization of vinyl acetate, for inclusion in liquid ocular formulations.

Effect of different polymer lattices on performance of their modified rapid hardening sulphoaluminate cement mortars

An emulsifier free latex (FL) and a conventional latex (CL) having the same chemical components were successfully synthesised with styrene (St) and butyl acrylate (BA) in the presence or absence of emulsifier. Properties of the polymer latex modified rapid hardening sulphoaluminate cement mortars, such as fluidity, air content, compressive strength, flexural strength and water absorption, were assessed and discussed. Test results show that FL has a superior effect on the properties of the polymer latex modified mortars compared with CL except at a polymer/cement ratio of 15%.

Investigating the Location of Propyl Gallate at Surfaces and Its Chemical Microenvironment by 1H NMR

The location and the resulting chemical microenvironment of the antioxidant propyl gallate (PG) was studied in micellar solutions using the cationic emulsifier cetyl trimethyl ammonium bromide (CTAB), the anionic emulsifier sodium dodecyl sulphate (SDS) and the non-ionic emulsifier Brij 58 (polyoxyethylene-20-cetyl ester). T (1) relaxation time of the aromatic protons of PG was investigated in micellar solutions and compared with that in aqueous solution in the absence of emulsifier. The relaxation time of the PG portion that is solubilized in the micelle (T (1,eff)) was calculated from the partition behavior of PG in micellar solution. From the 1D-(1)H spectrum, the alteration in the electron density of the aromatic protons and the alteration in the peak shape of the emulsifier headgroup and alkyl chain proton signals were indicative of the location of propyl gallate in the different micelles. Nuclear Overhauser effects (NOE) made it possible to deduce the exact location of PG by calculation of the relative NOEs. Marked differences were found for the location of PG in CTAB, SDS and Brij 58 micelles. PG was found to be located in the palisade layer of CTAB micelles, in the region of the polyoxyethylene chain of Brij micelles and in the Stern layer of SDS micelles. For careful study of the location of antioxidants and therefore to be able to characterize the chemical microenvironment of the antioxidants is crucial for understanding differences in antioxidant activities as a function of lipid surfaces. The application of spectroscopic methods may help to optimize the antioxidant activity to inhibit lipid oxidation at surfaces that are formed in a wide range of foods (emulsions), cosmetics, pharmaceuticals (emulsions and carrier systems) and of biological membranes (LDL-particles).

EFFECTS OF EMULSIFIERS ON CRYSTALLIZATION PROPERTIES OF LOW‐MELTING BLENDS OF PALM OIL AND OLEIN

ABSTRACT The effects of sorbitan tristearate (STS) and soy lecithin on palm oil and on palm olein blends with low slip melting points for fluidized palm oil formulation, by temperature cycling, were studied. The dispersion of crystals in the liquid influenced the viscosity and the solid fat content (SFC) of the product at the end of the temperature cycling treatment. The fluidized palm oil formulations were melted at 80C. STS and lecithin were added; the formulation was cooled at 20C for 80 min, was heated at 30C for 45 min and was cooled again at 20C for 30 min to reproduce the production temperatures of fluid shortening. The crystal development, SFC and viscosity were determined. Fine crystal aggregates were produced using 0.09% STS and 0.03% lecithin. Generally, however, lecithin produced uniform crystal aggregates. Crystal growth in the absence of emulsifier was limited, while the addition of emulsifiers increased the growth. Lecithin produced higher SFC than STS at 0.03%. STS was a crystal inhibitor in blends with much lower melting triacylglycerol. Lecithin and STS had little effect on viscosity: 0.06 and 0.09%, respectively. Thus, emulsifiers could be useful agents for controlling crystallization in fluidized palm oil formulations.

Particle morphology and NMR structure of polymethylmethacrylate/polystyrene emulsifier‐free core–shell cationic latices in the presence of DBMEA

AbstractIn the absence of emulsifier, we prepared stable emulsifier‐free polymethylmethacrylate/polystyrene (PMMA/PSt) copolymer latex by batch method with comonomer N,N‐dimethyl, N‐butyl, N‐methacryloloxylethyl ammonium bromide (DBMEA) by using A1BN as initiator. The size distribution of the latex particles was very narrow and the copolymer particles were spherical and very uniform. Under the same recipe and polymerization conditions, PMMA/PSt and PSt/PMMA composite polymer particle latices were prepared by a semicontinuous emulsifier‐free seeded emulsion polymerization method. The sizes and size distributions of composite latex particles were determined both by quasi‐elastic light scattering and transmission electron microscopy (TEM). The effects of feeding manner and staining agents on the morphologies of the composite particles were studied. The results were as follows: the latex particles were dyed with pH 2.0 phosphotungestic acid solution and with uranyl acetate solution, respectively, revealing that the morphologies of the composite latex particles were obviously core–shell structures. The core–shell polymer structure of PMMA/PSt was also studied by 1H, 13C, 2D NMR, and distortionless enhancement by polarization transfer, or DEPT, spectroscopy. Results showed that PMMA/PSt polymers are composed of PSt homopolymer, PMMA homopolymer, and PMMA‐g‐PSt graft copolymers; results by NMR are consistent with TEM results. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1681–1687, 2005

Synthesis and properties of soap-free poly(methyl methacrylate-ethyl acrylate-methacrylic acid) latex particles prepared by seeded emulsion polymerization

In order to obtain functional polymer latex particles with clean surface and with surface carboxyl groups, P(MMA-EA) seed particles with the diameter of 335 nm were first synthesized via soap-free batch emulsion polymerization of methyl methacrylate (MMA) and ethyl acrylate (EA), and then the seeded emulsion copolymerization of MMA, EA and MAA (methacrylic acid) onto the seed particles were performed in the absence of emulsifier. Influences of ingredients and conditions on polymerization, latex particle size ( D p ) and its distribution were investigated. Results showed that most of the monomers polymerized onto the seed latex particles in the second step of polymerization by using drop-wise addition method, and D p increased from 483 nm to 829 nm with the mass ratio of core/shell monomers [C]/[S] decreased from 1:2 to 1:15. It was found that D p decreased with the increase of MAA and initiator amounts, and the size of the latex particles became uniform with the decrease of MAA amount and with the increase of [C]/[S] value.

Interactions in dispersions of sugar particles in food oils: influence of emulsifier

The influence of oil-soluble surface-active components on the interactions of fine sugar particles dispersed in triglyceride oils has been investigated at different volume fractions by a combination of rheological and sedimentation experiments. Four different types of food oil were investigated: soybean, milk fat, lauric fat (palm kernel oil) and cocoa butter. The addition of a low concentration of emulsifier, soya lecithin (phosphatidylcholine) or monoolein, was used to adjust the nature of the interactions between the hydrophilic sugar particles. In a dispersion of 70 wt% sugar and 0.3% of lecithin, around 30–40% of the emulsifier present was found to be adsorbed at the surface of the sugar particles. The viscosities of the dispersions in the different oils were found to be similar up to 30 wt% sugar content. At high sugar contents (30–60 wt%), however, differences between the oil samples were evident. Lauric fat generated the highest viscosity amongst the different oils whereas cocoa butter exhibited the lowest. The presence of the emulsifier lowered the viscosity of the dispersions to differing extents. Gravity settling observations were made for dispersions of 10 wt% sugar particles in the different oils in the presence and absence of emulsifier. The emulsifiers were effective in reducing the volume of sediment and hence in increasing the sediment particle packing density. This implies that the adsorbed surface-active species reduce the strength of the attractive interactions between the sedimenting sugar particles, in good agreement with the rheological data at high sugar contents.

Investigation into the effect of carboxylic acid monomer on particle nucleation and growth in emulsifier-free emulsion copolymerization of styrene–butadiene–acrylic acid

Latexes of carboxylated styrene–butadiene rubber were prepared via batch emulsion copolymerization with different amounts of acrylic acid in the absence of emulsifier. The effect of acid monomer was investigated in the particle formation and growth. It was observed that the amount of acrylic acid strongly affected the particle formation. The number of particles and thus polymerization rate increased with increasing of the acid content. There was no significant difference in the polymerization rate per particle in all experiments. The results show that in this case particle growth process is less dependent on the acrylic acid amount in comparison with its influence on nucleation stage and then particle number. Several parameters such as polymerization rate and number of latex particle per unit volume of the aqueous phase were calculated. Attempt was made to evaluate the average number of growing chain per particle. Also average particle diameter of the above carboxylated SBR latexes was obtained through some calculations from the direct measurement of average particle diameter in the swollen state by light scattering technique for the first time.

Emulsion Copolymerization of Butyl Acrylate with Watersoluble Monomers in the Absence of Emulsifier

Paper has connection with emulsion copolymerization of butyl acrylate with water soluble monomers in the absence of emulsifier. It was measure of kinetics of this reaction for different conditions and mechanism of this reaction is discussed.

Size control of polystyrene beads by multistage seeded emulsion polymerization

Micron-sized monodisperse crosslinked polystyrene (PS) beads have been prepared by a multistage emulsion polymerization using styrene monomer, divinylbenzene crosslinking agent, and potassium persulfate initiator in the absence of emulsifier. In the first stage of the reaction, the lower the reaction temperature, the larger the bead size obtained. In the later stages of the reaction, the particle size is increased with the initiator concentration and monomer content. Particle nucleation of the preexisting polymer seed of 0.7–0.8 μm in diameter is prepared at 60°C, then the monodisperse crosslinked PS beads > 2 μm are synthesized up to the third stage of the reaction. As the particle size grows, the number of free radicals in the growing particles increases, and the conversion of the next stage is continuously increased. The reaction mechanism is suggested that the continuous polymerization be conducted due to the diffusion of monomer into the preexisting particles to induce spherical beads in the later stages of the reaction. Otherwise, phase separation or the formation of protrusion by the capture of free radicals will be taking place. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 2259–2269, 1999

Characterization of crosslinked polystyrene beads and their composite in SBR matrix

AbstractMonodisperse crosslinked polystyrene (PS) beads were prepared by a reaction of semibatch emulsion polymerization with styrene monomer, divinylbenzene (DVB) crosslinking agent, and potassium persulfate (K2S2O8) initiator in the absence of emulsifier. The glass transition temperature (Tg) and the mean diameter of the beads were increased from 100 to 135°C and from 402 to 532 nm, respectively, for an incorporation of 2–10 mol % DVB. Crosslinking density was also linearly increased with DVB content. Scanning electron microscopy (SEM) photographs of styrene–butadiene rubber (SBR) composite filled with various contents of PS beads revealed that PS beads are relatively well dispersed without changing the spherical shape of the beads in all ranges of compositions. In stress–strain analysis, elongation at break and tensile strength of SBR composite were increased with the bead content. Applicability of the PS beads as a filler in SBR matrix is tested by plotting Mooney–Rivlin or Guth–Smallwood equations. However, mechanical properties of the composite with the beads were not so excellent as those of the composite with carbon black. Crosslinked PS beads are still tentative as a white color reinforcing filler on the SBR matrix. © 1995 John Wiley & Sons, Inc.

Effect of electrolyte type on the electrokinetic behavior of sulfonated polystyrene model colloids

Sulfonated polystyrene latex particles were prepared by a two-stage “shot-growth” emulsion polymerization process in the absence of emulsifier. Sodium styrene sulfonate (NaSS) was used as an ionic co-monomer to produce a series of latex particles with the same particle size but with different surface charge densities. The electrophoretic mobility of this functionalized model colloid was studied in the presence of various types of inorganic electrolytes. The μe curves of these latexes exhibit a pronounced maximum at high electrolyte concentrations: 5·10−2 M for 1∶1 electrolytes and 10−2 M for 2∶1 and 1∶2 electrolytes. When a 3∶1 electrolyte (LaCl3) was used, the electrophoretic mobility changed to positive values at high concentration due to the specific adsorption of lanthanum species. The experimental results for the electrokinetic characterization of these sulfonated polystyrene model colloids suggest that the surface of the particles is covered by a layer of oligomers or polymer chains which shift the shear plane toward the bulk solution, increasing the anomalous surface conductance of the polystyrene microsphere-electrolyte solution interface.

Effect of some sodium bisulfite adducts of different chain lengths on the course of the emulsion polymerization of vinyl acetate

AbstractThe emulsion polymerization of vinyl acetate using some bisulfite adducts of different chain lengths with potassium persulfate as the redox initiation system, in the absence of emulsifier, was studied. The effects of such adducts, which contain the same weight equivalent of bisulfite anion, on the rate of polymerization, maximum conversion, and stability of the produced polymer lattices as well as the morphological characteristics including volume‐average diameters and the number of polymer particles per unit volume of water were investigated. The rate of polymerization was found to be dependent on the concentration of benzaldehyde, acetaldehyde, octyl aldehyde, methyl propyl ketone, and acetone sodium bisulfite adducts to the powers 0.54, 0.66, 0.95, 1.0, and 1.1, respectively. Also, it was found that increasing adduct chain lengths decreases the volume‐average diameter, increases the obtained lattice stability, and improves the morphology of the polymeric particles, where a spherical morphology and extra stability were obtained in the presence of the octyl aldehyde adduct. © 1993 John Wiley & Sons, Inc.This article is a US Government work and, as such, is in the public domain in the United States of America.

Model filled polymers. XI. Synthesis of monodisperse crosslinked polymethacrylonitrile beads

AbstractMonodisperse polymethacrylonitrile beads of varied size and crosslink density are prepared by emulsion copolymerization of methacrylonitrile and allylmethacrylate in the absence of emulsifier. The particle size is very sensitive to polymerization temperature and initiator concentration. Because of a nitrile group effect, the maximum conversion varies with reaction conditions. The highest conversion obtained was 82%. © 1992 John Wiley & Sons, Inc.